Supramolecular interaction between N-methylfulleropyrrolidine and porphyrazine studied in solution

Supramolecular interaction of N-methylfulleropyrrolidine (A) with a free-base porphyrazine (H₂Pz) is investigated in toluene. The interaction between A and H₂Pz is favored by charge transfer (CT), as the CT absorption band for the A-H₂Pz system is located at 533 nm. Utilizing the CT absorption maxima, some important physicochemical parameters are evaluated in the present work. The binding constant (K) of the A-H₂Pz system is determined both from UV-vis (K_UV-vis = 29640 dm³· mol⁻¹) and steady-state fluorescence measurements (K_fluorescence = 15440 dm³ · mol⁻¹). Lifetime measurement measures the value of the rate constant of charge separation and quantum yield of charge separation of the A-H₂Pz system, which supports the rationale of CT at the ground state. Hybrid-DFT calculations by the B3LYP method, extend very good support in favor of the K value of the A-H₂Pz system in terms of the heat of formation value, i.e., 0.57 kcal · mol⁻¹, and it provides excellent corroboration between the experimentally obtained CT energy (i.e., 2.325 eV) and the theoretically obtained E_HOMO – E_LUMO value of the A-H₂Pz system (E_HOMO – E_LUMO = 2.330 eV). The present study envisages that H₂Pz may be suitably employed as an effective receptor for functionalized fullerene molecules in the near future.